Reproducing Copy-Paste issue from Firefox to Java on Ubuntu

Main.java

import java.awt.datatransfer.UnsupportedFlavorException;
import java.io.*;

import java.awt.Toolkit;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.DataFlavor;
import java.util.Arrays;
import java.util.Optional;

public class Main {
    public static void main(String[] args) throws IOException, UnsupportedFlavorException {
        Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
        Optional<DataFlavor> flavor = Arrays.stream(clipboard.getAvailableDataFlavors())
                .filter((flv) -> "java.io.Reader".equals(flv.getParameter("class")))
                .filter((flv) -> "text/html".equals(flv.getHumanPresentableName()))
                .findFirst();

        if(!flavor.isPresent()) {
            throw new IOException("No Reader containing text/html found.");
        }

        try (PrintWriter writer = new PrintWriter(new OutputStreamWriter(new FileOutputStream("test.txt"), "UTF-8"));
             BufferedReader reader = new BufferedReader((Reader) clipboard.getData(flavor.get()))) {
            String line;
            while ((line = reader.readLine()) != null) {
                writer.println(line);
            }
        }
    }
}